1. Field of the Invention
The present invention relates generally to the field of flow control and metering, and more specifically, to flow metering and distribution devices capable of metering out and prioritizing the remaining contents of a fluid reservoir.
2. Description of the Related Art
For certain types of fluids necessary for mechanical locomotion, exhausting the supply of fluid, such as fuel, hydraulic fluid, or lubricant, can lead to adverse consequences. Conventional fluid reservoirs have an outlet in the bottom of the reservoir or have an outlet pipe or hose extending into the reservoir to terminate on or near the bottom. In either case, when the fluid level inside the reservoir reaches the outlet, the fluid delivery rate very suddenly changes from an operating flow rate to zero. As an example relative to engine lubrication, a lube line rupture, scavenge pump failure and other traumatic events can cause a jet engine to lose lubricant at a rate approaching the delivery rate of the main pump. At the normal operating flow rate, the supply of lubricant will be quickly exhausted. Operation with no lubricant, which follows, will be for only a short time before total failure of non-lubricated parts and subsequent engine failure occurs.
Similarly, in the case of a fuel reservoir approaching an exhausted supply state, the moment the fluid level falls below the reservoir outlet, or opening of an outlet pipe extending into the reservoir, the engine will cease operating suddenly. Normally, rate of fuel consumption is a function of engine load. Engine load increases as rpms increase, and also as more engine accessories are powered by the engine. By reducing speed and/or turning off engine accessories, the remaining contents of a fuel reservoir can be consumed at a lower rate. However, the operator of the engine is not normally made aware of an eminent fuel exhaustion until after it is too late. While it is not uncommon to provide warning signals when a reservoir reaches a predetermined low level, the exact timing of exhaustion is uncertain since the rate of consumption and the exact remaining quantity are unknown. Moreover, upon failure of the warning light, the operator will have no warning of the impending exhaustion of fuel, other than the fuel gauge itself, and will be unable to take active conservation measures.